In this video, Motley Fool health care analyst David Williamson takes a look at three biotech stocks making moves today and what you should know about them. Sequenom (NASDAQ: SQNM) made a big jump today despite higher-than-expected losses because of continued interest in its MaterniT21 Down syndrome test. SciClone Pharmaceuticals (SCLN) released some disappointing numbers. And ISIS Pharmaceuticals (IONS 0.14%) is up 15% after a recent buy rec from Cowen, but Williamson warns that there are some mitigating factors around ISIS that should curb investors' enthusiasm.